Telephone-exchange system



(No Model.)

T. A. WATSON Telephone Exchange System. No. 234,154. Patented Nov. 9,1880.

s M /6W (0111mm N. PETERS. PHOTO-LITNDGRAPHEL WASHINGTON n C UNITED STATES PATENT OFFICE.

THOMAS A. WATSON, OF EVERETT, MASSACHUSETTS.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 234,154, dated November 9, 1880,

Application filed April 29, I880. (N 0 model.)

T 0 all whom it may concern Be it known that I, THOMAS A. WATSON, of Everett, county of Middlesex, Stateof Massachusetts, have invented an Improvement in Telephone-Exchange Systems, of which the following description, in connection with the accompanying drawing, is a specification.

My invention relates to the circuits and instruments in a telephone exchange system whereby the subscribers on several circuits radiating from a common central point may be connected with a single central-office indicator or telephone and enabled to speak directly to and inform the attendant there what connection is desired, and the said subscribers may be signaled from the central office and connected to talk with one another, all these communications being made over the same wires.

It is impracticable to have a large number of the usual closed telephonic circuits uniting in a single circuit, which may be denominated a union circuit, passing through a single central telephone of common construction, as the said circuits, together with the union circuit, would all form branches in which the currents would divide, making their effect too feeble in any one branch.

The simplest method of accomplishing the first of the above-mentioned results, or enablin g the several subscribers circuits to be directly connected with a single central instrument and enabling the subscribers to make their wants known there, is to have the subscribers circuits-normal] y open and as many of them as desired uniting at the central office and passing through a suitable indicator or telephone to the ground.

When a subscriber wishes to confer with-the central office, he, by a suitable switch or key, (herein shown as the usual automatieswitch,) makesa ground-connection through his telephone, thus placing it in circuit with the central-office one and enabling him to speak to the operator, who should be constantly listening there, at least during the busy portions of'theday, and at other times the subscriber can in any usual way operate an indicator or signal placed beyond the uniting-point of the various circuits, and thus call the operator to his telephone. Should a second subscriber close the circuit through his telephone while one is conferring with the central ofliee, there will be a divided circuit, a branch passing through the second telephone, so that the said second subscriber will by listening a moment become aware that the central operator is engaged, when subscriber number two will wait until number one is provided for, after which he may take his turn.

It is necessary that a subscriber with whom a communication is desired should be summoned by a signal, usually given from the central office, and with the instruments now in use such signals can only be given through a closed circuit. In order, therefore, to call the subscribers on theopen circuits, special instruments adapted to be operated in said circuits must be used. These instruments can be such as to give a signal directly, or to allow signaling apparatus of ordinary or suitable construction to be brought into action.

The signal apparatus to enable a signal to be given on an open circuit is shown in one instance as a condenser placed at the end of the circuit, which is thus open in respect to the currents used in transmitting sound by the telephonic instruments, but will allow sudden currents of high tension to affect the apparatus used for signaling. The signal may also be given by an electric chime, or an apparatus operated on the principle of the electroscope by electricity of high tension, which may be produced in any usual manner, as by friction or induction'coil. This method may be used advantageously when there is but one subscribers station on a circuit.

Another method is to employ a switch, which cuts out the open point or condenser and so alters the electrical condition of the line that the ordinary individual or other systems of signaling may be employed. The switch is preferably a polarized relay arranged to close a shunt-circuit around the open point without removing relay from the control of 5 the central'office.

In a separate application filed of even'date herewith I have shown a series of circuits which are normally'grounded through high resistances. These resistances prevent the too great division of the current among the several branches. This'result can be produced,

IOO

as therein stated, with a small number ot'circuits by the natural resistance ot' the branch circuits and the instrument in the branches. in said application,although closed circuits of suitable resistance are more particularly described, the use of open circuits and other means for enabling subscribers on a series of circuits to call or communicate with the operator at central ofiice by means of a common instrument at said ofiice are indicated, and, while these are not specificallyclaimed therein, claims are made broadly to include them.

The use of switches to cut out the high resistance or an open point on any line, as may be required for signaling purposes, is also claimed.

The present invention, therefore, does not cover, broadly, a series ot telephonic circuits centering in a common instrument at a celltral ofiice and adapted to prevent the division of the currents from said instrument, nor the use of switches in the several circuits for altering the electrical condition of said circuit when these are open or grounded through high artificial resistance; but consists lll uniting a number of open circuits, or circuits connected with condensers, in a single instrument or union circuit, in adapting said circuits to receive audible signals, and in the use for closing the circuits through sllllllts around theopen points or condensers or around high resistances of polarized relays,these having special advantages ill connection with open circuits, but being obviously applicable as well to circuits grounded through high resistances.

The drawing shows, in diagram, severalcircnits uniting in a single central instrument, all arranged and provided with apparatus in accordance with my invention.

In practice t'orty or fit'tycircuitswill usually be centered in a single central telephone or indicating-instrumcnt; but four circuits, 1 2 34, only are herein shown, all uniting in a common conductor or union circuit, 5, passing through a single central telephone, a, to the ground. An indicating or signaling iiistrument, b, and battery h to operate it are also provided, which may be placed in the union circuit when an operator is not constantly listening at the telephone a, the circuit being closed through the telephone a or indicator 1) by a suitable switch, 0.

Telephones (l are shown at various stations on the circuits 1 I. 3 4, supported on the usual switch-hooks, which are shown as adapted to close the circuit directly to the ground, and thus throw the subscribers telephone into circuit with the central telephone, a, or, when the switch 0 is in the proper position, close the circuit of the battery I) through the indicator-magnet and operate the indicator 1). The switches at all the subscribers stations for making the said ground-connections are normally open, and the circuits are shown also as open at their outer end.

The circuit 2 is shown as having but a single subscribers station situated at its outer open end. With such an arrangement a signal can be operated by electricity of high tension by an apparatus similar to an electroscope, two metal balls, 0 f, being connected to the extremity of the line, and when charged with electricity are repelled by one another and strike the bells h 2', which discharge the said electricity, when the operation may be repeated. A similar effect would be produced by connecting one of the bells h or i with the line and the other withthe ground, the circuit being open and a single ball, 0, suspended between them, and when the line is charged with electricity of high tension the said ball will vibrate between the two bells in a wellknown manner. These connections are shown in dotted lines.

The circuits 1,15, and 4 are shown as having two subscribers stations, and terminate in one of the series of plates of a condenser, It, the other series of which is connected with the ground.

In circuits 1 and 4 apolarized relay, 1', or switch is shown for cutting out the condenser, so as to enable usual signal mechanism to be operated. The ground wire from the condenser passes through the coils of the relay. The armature ot' the relay is connected with the ground-wire between the condenser and the relay-coils, and one contact (the left-hand contact, as shown) is connected with the linewire on the opposite side of the condenser. The relay should be adjusted so that the armature remains on either contact until shifted by a current of the opposite polarity. When the armature rests upon the left hand or line contact a circuit is completed around the condenser through the coils of the magnet to ground. By shifting the armature this shuntcircuit is broken and the lilfe restored to its normal condition. In circuit3 signal-instrw ments properly adjusted to the work required would be use The condensers at the ends of the circuits permit the circuits and signaling-instruments therein to be afi'ected by sudden changes in electrical condition, but do not allow the force of the fluctuations used in talking to be divided among the branch circuits, and consequently have their effect weakened in any one branch. In their effect on a steady batterycurrent the condensers are open points, stopping the flow of the said currents, and thus enable the indicator b to be operated by the battery b as soon as a direct ground-connection is made on any of the blank circuits.

When two or more stations are located on the same circuit they may be signaled separately by the aid ot'signal mechanism, of which many varieties are now known. 0n circuits 1 and 4 no charge in those having signal mechanism controlled by step-by-step movements would be required. In other cases they might be suitably modified.

When a subscriber closes the circuit through his own and the central telephone he should listen a moment to hear if the central operator is engaged with another subscriber, and if so he may wait until their conversation is finished, and then himself address the central operator. If he hears nothing he may immediately make his own wants known. When a communication is desired between subscribers on different circuits the said circuits may be connected in any usual manner at the central office.

I am aware that the subscribers on several circuits have been connected directly with a single central-office telephone, but by an independent circuit additional to those used for intercommunication between the subscribers.

I claim- 1. In a telephone-exchange system, a series of normally-open subscribers circuits, all passing through a single central instrument, and adapted to be closed at any subscribers station through an instrument at said station and the central instrument, and apparatus used in conjunction with said subscribers circuit adapted to operate or control an audible signal, substantially as described.

2. A series of telephonic circuits, all passing through a single instrument at a central station to the ground, each circuit having one or more subscribers stations located therein,

provided with a circuit-closer normally open, to make a ground-connection when desired, and condensers at the extremities of the said circuit to allow a variation in the tension of an electric current to affect the instruments in the said circuit and prevent the passage of steady currents, substantially as described.

3. The combination, with a single telephonic instrument, of a series of telephonic circuits, all centering in and passing through the said instrument, substantially as described, said circuits being normally open or practically open with respect to the currents employed for telephonic communication, as set forth.

4. In an exchange system, the combination, with a number of line-circuits centering in a union or common instrument circuit at a central office and adapted to prevent the division of currents from one circuit into the others, of polarized relays located at the ends of said circuits and operating to ground the latter as required through branches of small resistance, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

THOMAS A. WATSON.

Witnesses:

Jos. P. LIVERMORE, N. E. O. WHITNEY. 

